[PATCH v7 5/5] loop: Add support for provision requests

Sarthak Kukreti
2023-05-22T22:10:14Z

On Mon, May 22, 2023 at 9:37 AM Darrick J. Wong <djwong@kernel.org> wrote:
>
> If someone calls fallocate(UNSHARE_RANGE) on a loop bdev, shouldn't
> there be a way to pass that through to the fallocate call to the backing
> file?
>
> --D
>

Yeah, I think we could add a REQ_UNSHARE bit (similar to REQ_NOUNMAP) to pass down the intent to the backing file (and possibly beyond...).

I took a stab at implementing it as a follow up patch so that there's less review churn on the current series. If it looks good, I can add it to the end of the series (or incorporate this into the existing block and loop patches):

From: Sarthak Kukreti <sarthakkukreti@chromium.org>
Date: Mon, 22 May 2023 14:18:15 -0700
Subject: [PATCH] block: Pass unshare intent via REQ_OP_PROVISION

Allow REQ_OP_PROVISION to pass in an extra REQ_UNSHARE bit to
annotate unshare requests to underlying layers. Layers that support
FALLOC_FL_UNSHARE will be able to use this as an indicator of which
fallocate() mode to use.

Signed-off-by: Sarthak Kukreti <sarthakkukreti@chromium.org>
---
block/blk-lib.c | 6 +++++-
block/fops.c | 6 +++++-
drivers/block/loop.c | 35 +++++++++++++++++++++++++++++------
include/linux/blk_types.h | 3 +++
include/linux/blkdev.h | 3 ++-
5 files changed, 44 insertions(+), 9 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 3cff5fb654f5..bea6f5a700b3 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -350,6 +350,7 @@ EXPORT_SYMBOL(blkdev_issue_secure_erase);
* @sector: start sector
* @nr_sects: number of sectors to provision
* @gfp_mask: memory allocation flags (for bio_alloc)
+ * @flags: controls detailed behavior
*
* Description:
* Issues a provision request to the block device for the range of sectors.
@@ -357,7 +358,7 @@ EXPORT_SYMBOL(blkdev_issue_secure_erase);
* underlying storage pool to allocate space for this block range.
*/
int blkdev_issue_provision(struct block_device *bdev, sector_t sector,
- sector_t nr_sects, gfp_t gfp)
+ sector_t nr_sects, gfp_t gfp, unsigned flags)
{
sector_t bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
unsigned int max_sectors = bdev_max_provision_sectors(bdev);
@@ -380,6 +381,9 @@ int blkdev_issue_provision(struct block_device *bdev, sector_t sector,
bio->bi_iter.bi_sector = sector;
bio->bi_iter.bi_size = req_sects << SECTOR_SHIFT;

+ if (flags & BLKDEV_UNSHARE_RANGE)
+ bio->bi_opf |= REQ_UNSHARE;
+
sector += req_sects;
nr_sects -= req_sects;
if (!nr_sects) {
diff --git a/block/fops.c b/block/fops.c
index be2e41f160bf..6848756f0557 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -659,7 +659,11 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
case FALLOC_FL_KEEP_SIZE:
case FALLOC_FL_UNSHARE_RANGE | FALLOC_FL_KEEP_SIZE:
error = blkdev_issue_provision(bdev, start >> SECTOR_SHIFT,
- len >> SECTOR_SHIFT, GFP_KERNEL);
+ len >> SECTOR_SHIFT, GFP_KERNEL,
+ (mode &
+ FALLOC_FL_UNSHARE_RANGE) ?
+ BLKDEV_UNSHARE_RANGE :
+ 0);
break;
case FALLOC_FL_ZERO_RANGE:
case FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE:
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 7fe1a6629754..c844b145d666 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -306,6 +306,30 @@ static int lo_read_simple(struct loop_device *lo, struct request *rq,
return 0;
}

+static bool validate_fallocate_mode(struct loop_device *lo, int mode)
+{
+ bool ret = true;
+
+ switch (mode) {
+ case FALLOC_FL_PUNCH_HOLE:
+ case FALLOC_FL_ZERO_RANGE:
+ if (!bdev_max_discard_sectors(lo->lo_device))
+ ret = false;
+ break;
+ case 0:
+ case FALLOC_FL_UNSHARE_RANGE:
+ if (!bdev_max_provision_sectors(lo->lo_device))
+ ret = false;
+ break;
+
+ default:
+ ret = false;
+ }
+
+ return ret;
+}
+
+
static int lo_fallocate(struct loop_device *lo, struct request *rq, loff_t pos,
int mode)
{
@@ -316,11 +340,7 @@ static int lo_fallocate(struct loop_device *lo, struct request *rq, loff_t pos,
struct file *file = lo->lo_backing_file;
int ret;

- if (mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE) &&
- !bdev_max_discard_sectors(lo->lo_device))
- return -EOPNOTSUPP;
-
- if (mode == 0 && !bdev_max_provision_sectors(lo->lo_device))
+ if (!validate_fallocate_mode(lo, mode))
return -EOPNOTSUPP;

mode |= FALLOC_FL_KEEP_SIZE;
@@ -493,7 +513,10 @@ static int do_req_filebacked(struct loop_device *lo, struct request *rq)
case REQ_OP_DISCARD:
return lo_fallocate(lo, rq, pos, FALLOC_FL_PUNCH_HOLE);
case REQ_OP_PROVISION:
- return lo_fallocate(lo, rq, pos, 0);
+ return lo_fallocate(lo, rq, pos,
+ (rq->cmd_flags & REQ_UNSHARE) ?
+ FALLOC_FL_UNSHARE_RANGE :
+ 0);
case REQ_OP_WRITE:
if (cmd->use_aio)
return lo_rw_aio(lo, cmd, pos, ITER_SOURCE);
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index b7bb0226fdee..1a536fd897cb 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -423,6 +423,8 @@ enum req_flag_bits {
*/
/* for REQ_OP_WRITE_ZEROES: */
__REQ_NOUNMAP, /* do not free blocks when zeroing */
+ /* for REQ_OP_PROVISION: */
+ __REQ_UNSHARE, /* unshare blocks */

__REQ_NR_BITS, /* stops here */
};
@@ -451,6 +453,7 @@ enum req_flag_bits {
#define REQ_FS_PRIVATE (__force blk_opf_t)(1ULL << __REQ_FS_PRIVATE)

#define REQ_NOUNMAP (__force blk_opf_t)(1ULL << __REQ_NOUNMAP)
+#define REQ_UNSHARE (__force blk_opf_t)(1ULL << __REQ_UNSHARE)

#define REQ_FAILFAST_MASK \
(REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 462ce586d46f..60c09b0d3fc9 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1049,10 +1049,11 @@ int blkdev_issue_secure_erase(struct block_device *bdev, sector_t sector,
sector_t nr_sects, gfp_t gfp);

extern int blkdev_issue_provision(struct block_device *bdev, sector_t sector,
- sector_t nr_sects, gfp_t gfp_mask);
+ sector_t nr_sects, gfp_t gfp_mask, unsigned int flags);

#define BLKDEV_ZERO_NOUNMAP (1 << 0) /* do not free blocks */
#define BLKDEV_ZERO_NOFALLBACK (1 << 1) /* don't write explicit zeroes */
+#define BLKDEV_UNSHARE_RANGE (1 << 2) /* unshare range on provision */

extern int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
sector_t nr_sects, gfp_t gfp_mask, struct bio **biop,
--
2.39.2